1. Field of the Invention
This invention relates to a sealed lead-acid battery, and particularly to a sealed lead-acid battery which is sealed by utilizing what is called an "oxygen cycle," i.e., the action of causing the oxygen gas that is evolved at the positive plate toward the end of charging to react with a negative active material.
2. Description of Prior Art
For a lead-acid battery to be sealed by the "oxygen cycle" the oxygen gas that is evolved toward the end of charging must be transported from the positive plates to the negative plates. In order to ensure this gas transport, a gelled electrolyte is used or absorption of the electrolyte by porous separators is adopted. Regarding the latter method, it has been recently reported that the porous separators are not completely filled with the electrolyte and voids for the transport of the oxygen gas from the positive plates to the negative plates are present in the porous separators.
The idea of using these porous separators in the sealed lead-acid battery is disclosed, for example, in U.S. Pat. No. 3,862,861. It states that the sealed lead-acid battery disclosed in characterized in one aspect by the hypothesis that the porous separators have a higher capacity for absorption of electrolyte than the plates and the electrolyte within the plates is present in the form of a thin film wrapped around particles of active materials. According to this disclosure, it is inferred that the electrolyte is substantially present within the separators. With a view to improving the high rate discharge characteristics, this U.S. patent contemplates reducing the discharge current density by using thin flexible "non-self-supporting" grids. To preclude the "non-self-supporting" grids from shortening the battery service life, the plate assembly is wound under exceedingly high pressure.